Ink knife for the ink duct roller of a printing machine

ABSTRACT

A process is disclosed for producing an ink knife for the ink duct roller of a printing machine from an at least about 2 mm thick metal plate. Parallel slits are formed which extend from the working edge of the ink knife over part of the plate width and form lamellas of color zone width. Parallel transverse and blind-ended grooves which start at the working edge are first cut into the metal plate at intervals which correspond to the width of the color zones. Afterwards, a continuation rating groove that extends parallel to the working edge is cut in the area of the blind ends of the transverse grooves, preferably on at least one side of the metal plate. Finally the metal plate is completely cut through in the area of the transverse grooves, preferably by means of laser beams, forming a narrow slit at intervals which correspond to the width of the color zones.

BACKGROUND OF THE INVENTION

The invention relates to a process for production of an ink knife for anink duct roller of a printing machine from a metal plate at least 2 mmthick, where parallel slots are formed which extend at right angles fromthe working edge of the ink knife over part of the plate width and formblades of ink zone width.

Multiple-blade ink knives are known for example from CH-A5 602345. Thisink knife has in the area of the working edge recesses which lie on bothsides of adjustment screws next to the blades. The blades can beadjusted individually, a mechanical influence on the adjacent blade areais excluded or at least substantially reduced. The thickness of the inklayer can be set on each blade, individual ink amounts in the differentink zones can be changed as required by the printing image in thedifferent ink zone widths. The disadvantage of this solution is theintermediate spaces between the blades which allow the passage of evenhigh viscosity inks and the formation of annular rings on the inkductor.

According to the known state of the art, various measures are proposedwhich prevent at least in part the penetration of ink into the slots butalways entail other disadvantages.

According to DE, A1 2228625, the slots between the blades of an inkknife are filled with a plastic. This mechanically decouples adjacentblades thanks to the elasticity of the plastic. As the usage periodincreases however there is an increasing risk that parts of the plastic,in particular when a blade is greatly deflected in comparison with itsneighbor, will come loose and harm the print quality.

Numerous design forms are known according to which the slots between theblades of an ink knife are covered either with a metal or with a plasticfoil, for example according to U.S. Pat. No. 2837024. These cover foilsare effective but cause substantial problems for example as a result ofwear and penetration of the ink between the foil and the blades.

In DE, C1 3525589, the working edge of an ink knife is slotted with awire erosion machine or with laser beams. An adhesive coating of amaterial softer than the ink knife has a greater thickness than thewidth of the slot. When the blade is adjusted, the excess material iscut away and the slot completely closed. The penetration of ink into thenarrow slot is prevented with complex measures.

According to EP, B1 0376885, ink knives are produced which have slotsformed by laser beams of a width of 0.1 to 0.3 mm, which preventsleakage without additional cover in the case of high viscosity printinginks. In addition to the defined slot widths, the ink knife must havethe following properties:

The slots must be longer than half the plate width but must not exceedtwo-thirds thereof.

The thickness of the plate must be at least twice the maximum adjustmentpath of the blades.

Preferred plate thicknesses are 1 to 3 mm. It has been shown that in thethicker plate range extremely narrow slots from 0.01 to 0.03 mm widthcan only be cut out cleanly and regularly with great difficulty, if atall. Furthermore this solution is limited to high viscosity inks.

SUMMARY OF THE INVENTION

The present invention is based on the task of creating a process of thetype described above which considerably facilitates and rationalizes theproduction of narrow slots in particular with laser beams. In particularwith a metal plate thickness of at least 2 mm, an extremely narrowregular cut can be made with laser beams and the blades formed, despitetheir thickness, can be adjusted with appropriate use of force.Furthermore there is the option of preventing or at least reducing byadditional means the harmful consequences of ink of a lower viscosityrange penetrating the slot.

The task is solved according to the present invention in that:

(a) blind-ended, parallel, transverse grooves are cut out of the metalplate at intervals corresponding to the ink zone width, starting fromthe working edge, and

(b) the metal plate is cut through in the area of the transverse groovesto form a narrow slot at intervals corresponding to the ink zone width.

Special and further design forms of the process are the subject ofdependent patent claims.

The process according to the invention creates the possibility, evenwhen thick metal plates are used, of constructing ink knives withextremely narrow slots without the occurrence of technical problemswhich are difficult to solve. The thickness of the metal to be cutpreferably by the laser beam is always less than the thickness of themetal plate. This residual thickness is limited by the deflection of theblades on adjustment to an ink duct roller. As this adjustment path inpractice is relatively small, the transverse grooves can be formedcorrespondingly deep and hence facilitate the slot formation by thepreferred laser process.

Even with very great plate thicknesses, the mobility of the blades isalways guaranteed to the required extent as suitably at the blind slotend on at least one side of the metal plate a weakening groove ofselectable depth is provided.

However it is of essential importance that (b) is always carried outafter (a), otherwise the benefits of laser cutting through a thinnermetal layer cannot be exploited and this would no longer correspond tothe present invention.

The transverse grooves are preferably cut out at a width of 50 to 200%of the plate thickness at a depth of 20 to 80% of this plate thickness.For production of an ink knife, suitably a metal plate of spring steelis used which is 2 to 5 mm, in particular 3 mm thick. The depth of thetransverse grooves in this case is preferably in the range from 1 mm tod-1 mm, where d indicates the thickness of the metal plate.

The cross sectional form of the transverse grooves is not significant initself; in addition to rectangular, square, trapezoid, semi-circular orcircle segment shape, it can assume any other form suitable forproduction. Usually transverse grooves of rectangular section are milledout of a metal plate before or after the plate is hardened. Suitably ina subsequent working process the weakening groove is milled out of themetal plate on the same side.

The longitudinal weakening grooves can however also be cut out on bothsides of the plate. When formed on one and both sides, a semi-circularor circle-segment shaped cross section form is particularly suitable fora weakening groove. As indicated however the weakening groove can alsobe rectangular, square or even formed as a simple broad cutcorresponding to the cross section form of the transverse grooves.Depending on the adjustment force available for the blades on the inkduct roller, the weakening groove or grooves are recessed more or lessdeeply.

The slots usually produced with the laser beams between the bladessuitably have a width of maximum approx 0.1 mm, preferably max. 0.05 mm,in particular 0.01 to 0.02 mm. The narrower the slot, the less ink canpenetrate if this is not of high viscosity. In particular in the upperrange of slot widths, instead of the laser beams an equivalent processcan be used for example wire erosion.

According to a further design form of the invention, the transversegrooves are filled with an elastic mass which does not penetrate thegrooves. This ensures a perfect seal of the slots. This mass, in no casemetallic, preferably consists of a plastic, an acid resistant siliconmass or an inserted rubber profile, for example a rubber cord.Evidently, if required, the weakening groove can also be filled with theelastic mass.

According to a preferred design form of the invention, the transversegrooves in the metal plate are covered at least in the area of theworking edge with a first leg of an angled scraper. Its second freelyprojecting leg is bent or folded through an angle of preferably 30 to60°. The angled scraper consists for example of a 0.05 to 0.1 mm thickmetal plate or a plastic profile.

The first leg of the angled scraper is preferably glued to the blades ofthe metal plate. Thanks to the transverse grooves, the individual bladesfor adjustment have the necessary freedom of movement without mechanicaleffect on adjacent blades.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail using the design examplesshown in the drawings which show:

FIG. 1 a partial top view of an ink knife,

FIG. 2 a front view of FIG. 1,

FIG. 3 a side view of FIG. 1,

FIG. 4 an enlarged partial longitudinal section through the ink knife inthe area of the blades, and

FIG. 5 a partial side view of an ink knife with an angled scraper.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An ink knife 10 shown in FIGS. 1 to 3 essentially consists of a metalplate 12 of spring steel which has a width b of 90 mm and a thickness dof 3.5 mm. Starting from a working edge 14, transverse grooves 16running parallel are cut out at a right angle and have a depth t of 1.5mm and a width c of 2.5 mm. The transverse grooves extend over adistance a of approximately 35 mm in relation to width b of the metalplate 12.

In the longitudinal center plane of the transverse grooves 16 runs aslot 18 produced by laser beam said which is of 35 mm length and 0.015mm width and 2 mm depth which serves to form the blades.

In the area of the blind ends 20 of the transverse grooves 16, parallelto working edge 14, runs a recessed weakening groove 22 ofcircle-segment cross section. This has a radius of curvature ofapproximately 5 mm and is cut 1.5 mm deep, as are the transverse grooves16. Thanks to this weakening groove 22 the blades 24, which form an inkzone width f, can move vertically to the plane of metal plate 12 withlittle use of force.

FIG. 4 shows more clearly the slot 18 of width s 0.015 mm formed bylaser beam between the blades 24. The transverse grooves 16, againrectangular in cross section, are filled with an elastic mass 26, in thepresent case an acid-resistant silicon mass. An angled scraper 38 (FIG.5) is attached to the blades with an adhesive layer 28. Only the firstleg 30 of this angled scraper is visible in FIG. 4.

If the right blade 24 is pushed into the position 32 shown by dottedlines, for example by an adjustment screw not shown, the adjacent centerblade 24 is not moved with it in sympathy because the broad transversegroove 16 has a compensatory effect. If the transverse groove 16 wereonly narrow, the adjacent blade 24 would be moved in sympathy. Thenarrow slot s however persists even when the right blade 24 is moved.The residual material thickness d-t in the area of working edge 14 issufficiently large to keep slot 18 unchangingly narrow when a blade 24is moved in the direction of the blade plane. In other words theadjustment of the blades to change the quantity of ink supplied is neverso great that adjacent blades 24 shear away from each other and nolonger form slot 18.

FIG. 5 shows an ink knife 10 adjusted to an ink duct roller 34. Theblades of the ink knife 10, which is over 2 mm thick, are cut out by twolongitudinal weakening grooves 22 of circle-segment cross sectionrunning parallel to the working edge 14. The blades 24 are thus moremobile in the direction of arrow 36.

On the side of the blades 24 facing away from the ink duct roller 34, anangled scraper 38 is glued by its first leg 30 on to blades 24. The leg40 of angled scraper 38 projecting freely over 3 to 5 cm is folded aboutan angle a of slightly over 40°.

To summarize it can be found that in particular the following advantagescan be achieved with the present invention:

A metal plate 12 for production of an ink knife 10 has a thickness d ofover 2 mm, preferably over 3 mm. This avoids the deformation of theblades 24 on adjustment. The screws require no support plate.

Thanks partly to a longitudinal weakening groove 22, the relativelythick blades are mobile to the required extent in the area of workingedge 14.

The transverse grooves allow a very narrow slot which can easily beproduced with a laser beam and which can be adapted to the viscosity ofthe ink.

The broad transverse grooves allow, without mechanical effect on theadjacent blades, the arrangement of an angled scraper 38 which is gluedto the side of the metal plate 12 facing away from the ink duct roller34.

I claim:
 1. Process which comprises: producing an ink knife for an inkduct roller of a printing machine from a metal plate at leastapproximately 2 mm thick; forming narrow parallel slots which extendfrom a working edge of the ink knife over a part of the plate width (b),and forming blades of ink zone width (f), including the steps of(a)first, cutting blind-ended, parallel transverse grooves out of the metalplate at intervals corresponding to the ink zone width (f) starting fromthe working edge, and (b) then, cutting through the metal plate in thearea of the transverse grooves, including the working edge, to form saidnarrow slots at intervals corresponding to the ink zone width (f). 2.Process according to claim 1, wherein said narrow slots are formedsubstantially rectangular in shape and are formed having a maximum widthof approximately 0.05 mm for each slot.
 3. Process according to claim 1,wherein the transverse grooves are cut in a width (c) of 50 to 200% ofthe plate thickness (d), and a depth (t) of 20 to 80% of the platethickness (d).
 4. Process according to claim 1, wherein said transversegrooves are cut from a metal plate of thickness (d) of 2 to 5 mm, andwherein said transverse grooves are cut to a depth (t) of 1 to d-1 mm.5. Process according to claim 4, wherein the thickness of the metalplate is approximately 3 mm.
 6. Process according to claim 1, whereinsaid transverse grooves are cut out and have cross-sections selectedfrom the group consisting of rectangular, square, trapezoid,semi-circular and circle-segment shape.
 7. Process according to claim 1,wherein said transverse grooves are milled out of a metal plate, and aweakening groove is formed in said plate running parallel to the workingedge.
 8. Process according to claim 7, wherein said metal plate isspring steel.
 9. Process according to claim 1, wherein a weakeninggroove with depth (t) is cut out of the same side of the metal plate assaid transverse grooves.
 10. Process according to claim 9, wherein thedepth of the weakening groove corresponds to the depth of the transversegrooves.
 11. Process according to claim 1, wherein a laser beam producessaid slots of widths of 0.01 to 0.02 mm.
 12. Process according to claim1, wherein the transverse grooves are filled with an elastic mass whichdoes not penetrate the slots.
 13. Process according to claim 12, whereinsaid elastic mass is selected from the group consisting of anacid-resistant silicon mass and a rubber profile.
 14. Process accordingto claim 1, wherein the transverse grooves in the metal plate, at leastin the area of the working edge, are covered with a first leg of anangled scraper, where a second free leg of the angled scraper is bent orfolded about an angle.
 15. Process according to claim 14, wherein saidangle is from 30 to 60°.
 16. Process according to claim 1, wherein theslots are formed in the transverse grooves.
 17. Process according toclaim 1, wherein the first formed grooves are cut part way through theplate, and the second formed slots extend completely through the plate.18. Process which comprises: producing an ink knife for an ink ductroller of a printing machine from a metal plate at least approximately 2mm thick; forming narrow parallel slots which extend from a working edgeof the ink knife over a part of the plate width (b), and forming bladesof ink zone width (f), including the steps of(a) first, cuttingblind-ended, parallel transverse grooves out of the metal plate atintervals corresponding to the ink zone width (f) starting from theworking edge, and (b) then, cutting through the metal plate in the areaof the transverse grooves, including the working edge, to form saidnarrow slots at intervals corresponding to the ink zone width (f),andwherein the slots are produced with laser beams and a complete weakeninggroove is cut in the area of blind ends of the transverse groovesrunning parallel to the working edge.
 19. Process according to claim 18,wherein said weakening groove is cut on at least one side of the metalplate.